JPH0469012A - Protective method and device for superconducting coil - Google Patents

Abstract

PURPOSE:To protect a superconducting coil quickly by providing a single pole power supply to be connected across the superconducting coil through a disconnector, another power supply to be connected in parallel with the superconducting coil, and at least one protective resistor and a circuit opening means thereby eliminating a power switch for continuously feeding a large current. CONSTITUTION:A disconnector DS is normally closed to feed power from a single pole power supply E1 to a superconducting coil L thus exciting the superconducting coil L. Immediately upon quenching of the superconducting coil L, a first ON switch SW1 is closed to bring the voltage of the single pole power supply E1 to zero. Consequently, a thyristor Th is closed to bring the current of the power supply E1 quickly to zero. Current of the superconducting coil L is thereby commutated automatically to SW1-Ly-F. When the fuse F is blown out by the current commutated thereto, the current is interrupted and commutated to a protective resistor Rd1 which absorbs magnetic energy of the superconducting coil L thus protecting the superconducting coil L.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a protection method and a protection device for protecting a superconducting coil when quenching occurs in the superconducting coil.

[Prior art] Figures 3 (^) to (D) are, for example, published by the Institute of Electrical Engineers of Japan in 1982.
Figures 1 to 4 of the paper ``Improvement J of parallel resistance regeneration for quench protection of superconducting magnets'' published in IEEJ Transactions B, Vol. 102, No. 12, pages 73 to 79, published in December 2013. FIG.

In the conventional parallel resistance type protection device shown in FIG. 3(^), the cryostat CR consists of a superconducting coil and a resistance R(t) of a normal conductive portion generated in the superconducting coil L. Note that the resistance value of this resistance R(t) increases as time passes. A power source, for example, a unipolar power source E, is connected between both ends of the cryostat CR via a power switch S, and a protection resistor R is connected in parallel with the cryostat CR.

Donaldson ([1onaldson) in Figure 3 (B)
This is a protection device proposed by Mr. K., which uses a diode D instead of the protection resistor RD shown in Figure 3 (^), and also uses two switches S1 and s2 and three resistors R, , R2 and R3. In the end, it is a combination of parallel resistors in multiple stages.

Figure 3 (C) and <1)) are the protection devices proposed by Michiaki Nakano et al. in the paper mentioned above, and the former consists of two protection resistors R connected in series instead of the protection resistor RD.
a and Rb, and a capacitor C is connected in parallel with the protective resistor Rb, and the latter further has a series circuit consisting of an inductor Ls and a resistor Rs connected in parallel with the protective resistor Ra.

The protective devices shown in Figures 3(^)-(1)) and refined as described above all have basically the same drawbacks when compared to the present invention, so for the sake of simplicity they are described below. 3rd to
Only the operation of the protection device shown in Figure (^) will be explained.

During normal operation, when the power switch S is closed, most of the current from the power source E flows through the superconducting coil, but almost no current flows through the protective resistor RD due to its large resistance value.

However, when the superconducting coil L quenches,
Since energy is lost in this part, the temperature rises and the superconducting coil L is damaged. Therefore, it is necessary to quickly extract the energy stored in the superconducting coil L from the superconducting coil L. For that purpose, power supply E
While lowering the voltage, open the power switch S. Then, a large voltage Vc is generated across the power switch S,
This is also applied to the protective resistor RD, and the current flowing through the superconducting coil begins to flow as shown by arrow 1c.6 Then, the magnetic energy in the superconducting coil is converted into thermal energy by the protective resistor R9. The superconducting coils are protected as they are converted and released outside the cryostat.

[Problems to be Solved by the Invention] In conventional protection devices, a large current flowing through the superconducting coil always flows through the power switch, and the current had to be cut off with a high voltage when quenching. In fact, a superconducting plasma experimental device is being planned at the Ministry of Education's Institute for Fusion Science! (called LID) is always between 20 and 30 ^
The design is proceeding with parameters such that a current of 100 volts will flow and a voltage of 6 kV will be generated when the circuit is cut off. A power switch having such a rating has the problem of being extremely large and expensive.

This invention was made to solve this pressure point, and it does not use an extremely large and expensive power switch.
The object of the present invention is to provide a method and device for protecting a superconducting coil that can quickly commutate current through the superconducting coil.

[Means for Solving the Problems] A superconducting coil protection device according to the present invention includes a unipolar power source connected between both ends of the superconducting coil via a disconnector,
A separate power source, at least one protective resistor, and circuit opening means are provided, which are connected in parallel with the superconducting coil.

[Function] In this invention, during normal operation, current is passed from the unipolar power source to the superconducting coil, but not to the circuit opening means, and when the superconducting coil is quenched, the unipolar voltage is reduced to zero, and at the same time A separate power source is operated to make the current of the unipolar power source zero, and the current flowing through the superconducting coil is commutated to the circuit opening means, and then the disconnector is opened at the zero current point. The circuit opening means is opened to cut off the commutated current, and as a result, the superconducting coil current is commutated again to the protective resistor, thereby causing the magnetic energy accumulated in the superconducting coil to be absorbed by the protective resistor. 6 [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a circuit diagram for explaining an embodiment of the superconducting coil protection method and protection device according to the present invention. connected via the device DS. Protection resistance R
8l is the first ON switch SW + and inductor L
The protective resistor R8l is connected in parallel with the superconducting coil L through a series circuit consisting of P, but since the resistance value of the protective resistor R8l is usually large, the protective resistor RD1 may be directly connected in parallel with the superconducting coil. A fuse F, which is an example of circuit opening means, is connected in parallel with the protective resistor RD.

Also, as shown in the figure, a series rgJFI consisting of a charged capacitor C2, an inductor L2, and a thyristor Th
@ forms a separate power source E2, and this separate power source E2 is also connected in parallel with the superconducting coil L.

During normal operation, first close the disconnector DS and disconnect the unipolar power supply E.
1, the superconducting coil L is energized, and a predetermined current i is passed in the direction of the arrow to excite the superconducting coil L. At this time,
Since the first ON switch SW is open, fuse F
No current flows through.

Next, when a quench occurs in the superconducting coil, this is detected and the first ON switch SW1 is immediately closed, and
The voltage of the unipolar power supply E1 is set to zero. However, since the resistance value is low in such a circuit of superconducting coil L,
The current flows immediately from the first ON switch SW1 to the inductor L.
There is no commutation in the series circuit consisting of y→fuse F, so when the cyrisk Th is closed, the current flows out of the capacitor C2 and therefore from the separate power supply E2, immediately bringing the current of the unipolar power supply E1 to zero. At this time, since El is a unipolar power supply, the current does not flow in the opposite direction, so the superconducting coil L
The current is automatically commutated to SW+-Ly→F. At this time, the disconnector DS is opened at the current zero point. In this way, the opening/closing of the circuit device DS is always performed at the current zero point, and the large power switch S as in the conventional example is not required.

Next, a shutoff operation is performed. That is, the fuse F is blown by the current commutated to the fuse F, thereby cutting off the current. Then, the current is further commutated to the protective resistor Rd, where the magnetic energy of the superconducting coil L is absorbed and the superconducting coil is protected.

FIG. 2 is a circuit diagram for explaining another embodiment of the present invention, in which a protective resistor RDI is connected in parallel with a superconducting coil L via a first ON switch SW1. A DC breaker DCM as another example of circuit opening means is connected in parallel with the protective resistor RD1, and includes a first series circuit consisting of a fuse F and a breaker CB, and is connected in parallel with the first series circuit as shown in the figure in advance. A capacitor C1 charged with the polarity of , an inductor L for adjusting the time constant of the current flowing out from the capacitor C1, and a second ON switch SW.
, including a second series circuit consisting of a DC breaker D
In addition to the above-mentioned refined CMs, there are many examples of CMs shown in Table 5 on page 811 of the Electrical Engineering Handbook published by the Institute of Electrical Engineers of Japan on February 28, 1985. Also, R+]2 is connected in parallel with the protective resistor Ro1 for other protection.
and a third ON switch S W s are connected.

Although the insertion position of the disconnector DS in FIG. 2 is different from that in FIG. 1, this is not an essential change, but is just one embodiment. Similarly, although the inductor Ll is not shown in Fig. 2, it is used to effectively shunt the current from the capacitor C2 to the circuit section including the fuse F and the unipolar power supply E1, and the wiring etc. If it is included, as shown in FIG. 3, it is not particularly necessary.

During normal operation, first close the disconnector DS and disconnect the unipolar power supply E.
Since the superconducting coil is energized from 1 and the first ON switch SW1 is kept open, no current flows through the cutoff section of the DC breaker DCH, for example, the first series circuit described above. In addition, the disconnector CB is closed, the capacitor C1 is charged in advance to the polarity shown in the figure (by closing the disconnector DS, the first ON switch SW, and the second ON switch SW2, and passing through the inductor L), and then S W 2
and the third ON switch SW are left open.

Next, when a quench occurs in the superconducting coil, this is detected and the first ON switch SWI is immediately closed, and
The voltage of the unipolar power supply E1 is set to zero. Then, at the same time as the current in the superconducting coil L starts to decrease a little, the current in the unipolar power source E1 also decreases, and the current in the series circuit consisting of the first ON switch SW1→breaker CB→fuse F increases.

However, the current does not immediately flow to the first ON switch SW.
- There is no commutation in the series circuit consisting of L-breaker CB and fuse F. Therefore, when the thyristor Th is closed, current flows from the capacitor C2 and therefore from the separate power source E2, quickly reducing the current of the unipolar power source E1 to zero. Then, all the current in the superconducting coil L is automatically commutated to the above-mentioned series circuit.

At this time, the disconnector DS is opened at the current zero point. This electrically disconnects the unipolar power source El from the superconducting coil L and the series circuit described above.

Next, a shutoff operation is performed. That is, by closing the second ON switch SW2, the current from the capacitor C1 flows through the inductor L1 and the second ON switch SW2, causing the current in the breaker CB to rapidly decrease and eventually become zero. Then, when breaker CB is opened, breaker C
The current is interrupted without generating an arc between the electrodes of B.

By doing so, even if breaker CB fails to cut off the current, fuse F will cut it off.

Therefore, fuse F is connected to breaker CB.
It can be said that it serves as a backup for

As a result, the current from the superconducting coil L flows through the first ON switch SW1→protective resistor R6, and the energy of the superconducting coil L is absorbed by the protective resistor R01.

At this time, if you want the current to decay more slowly, the third O
The N switch SW may be closed so that a part of the current also flows through the protective resistor RD2. In this way the superconducting coils are protected.

[Effects of the Invention] As explained in detail above, the present invention provides a unipolar power source connected between both ends of a superconducting coil via a disconnector,
Since it is equipped with a separate power supply connected in parallel with the superconducting coil, at least one protective resistor, and a circuit opening means, a power switch (continuous rating) for constantly supplying a large current is not required, Furthermore, since commutation can be performed smoothly, the superconducting coil can be quickly protected.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram for explaining one embodiment of the present invention,
Figure 2 is a circuit diagram for explaining another embodiment, Figure 3 (
^) to (D) are circuit diagrams showing conventional protection devices. In the figure, L is a superconducting coil, El is a unipolar power supply, and R
2 is a separate power supply, Rol and R92 are protective resistors, F is a fuse, CB is a breaker, and DCM is a DC breaker. In addition, in the drawings, the same reference numerals indicate the same 5 or corresponding parts. Agent Zeng Ga Do Teru DS: Disconnector EI', ? #-3:! Juuzuin Ryo E2: Photo'1
Electric V all RDI: combined λbikitei 9th floor: same use゛' L-A Eimi special coil addition 2 figure RD2 ↓tE\Sairoku-

Claims (2)

[Claims] (1) A device equipped with a unipolar power source connected between both ends of the superconducting coil via a disconnector, a separate power source connected in parallel with the superconducting coil, at least one protective resistor, and circuit opening means. During normal operation, the disconnector is closed to allow current to flow from the unipolar power source to the superconducting coil, but not to the circuit opening means, and when the superconducting coil is quenched, the voltage of the unipolar power source is zeroed. At the same time, the separate power supply is operated to make the current of the unipolar power supply zero, and the current flowing through the superconducting coil is commutated to the circuit opening means, and then the disconnector is opened at the zero current point. and opens the circuit opening means to interrupt the commutated current, thereby causing the superconducting coil current to re-commute to the protective resistor, thereby transferring the magnetic energy stored in the superconducting coil to the A method of protecting a superconducting coil characterized by absorbing it into a protective resistor. (2) A unipolar power source connected between both ends of the superconducting coil via a disconnector, a separate power source connected in parallel with the superconducting coil, at least one protective resistor, and circuit opening means. A superconducting coil protection device characterized by: